Venous thromboembolism (VTE) is a common complication in patients with cancer principally in association with central vein catheters (CVC). The clinical benefit of antithrombotic prophylaxis for CVC-related VTE in cancer patients remains unclear.The aim of this study is to evaluate the efficacy and safety of the administration of Bemiparin in cancer patients with a central venous catheter (CVC). This study is designed as a multicenter, randomized, double-blind, placebo-controlled study. On the day of CVC insertion, eligible patients are randomly assigned to receive subcutaneously either bemiparin (3,500 UI/day) or placebo by using preloaded syringes for 45 days.